Operation & Troubleshooting
14
ACC-SVN136E-EN
Table 4.
Troubleshooting guide
Problem
Possible Cause
Possible Solution
No fan operation
No 24 volt control voltage
Check for 24 VAC at control and verify correct wiring.
If wired correctly, check voltage across the
transformer.
No line voltage
Check voltage across the FTB pins D and C. If no line
voltage is present, verify all wiring is correct.
Bad fan motor or controller
Disconnect power. Place the jumper removed during
installation back onto FTB-1/FTB-2 across terminals
(C) and (D). Restore power to the unit and check for
fan operation. If fan does not start, motor is bad and
should be replaced. If motor does start, check
controller settings. If motor still fails to start, replace
controller.
Improper fan operation
Heat pump jumper not configured correctly
Refer to the IOM or correct hook-up diagram and verify
the heat pump jumper is configured correctly.
Control is not wired correctly
See wiring diagrams. Ensure that the 24 VAC power
supply is connected in-phase with the motor power
supply.
No fan modulation
No need to modulate the fan
If pressure is equal to or greater than the head
pressure control setpoint, the fan will be operating at
full speed.
No input pressure to control
Check for proper transducer and Tee installation.
Schrader valve depressor must depress Schrader valve
enough to allow refrigerant into pressure transducer.
Heat pump inputs wired incorrectly into the controller
Check hook-up diagram and verify heat pump inputs
are properly wired into the controller.
Miswired
Verify jumper on FTB is removed
Check that the 24VAC signal and the transducer are
wired up correctly into the controller.
Erratic fan operation
Control is not wired correctly
See wiring diagrams.
Pressure transducer problem
Check for proper transducer and Tee installation.
Schrader valve depressor must depress Schrader valve
enough to allow refrigerant into pressure transducer.
Dirty or blocked condenser coil
Clean condenser coil.
Fan motor is cycling on thermal
overload
Dirty or blocked condenser coil
Clean condenser coil.
Wrong motor for fan speed control application
Verify new motor was installed. Replace with motor
approved for fan speed control application.
Unit fails to start
Incorrect/No voltage present
Using an AC voltmeter, measure the voltage between
the 24VAC terminals. It should read approximately 24
volts. Measure the line voltage between LINE1 and
LINE2 to confirm that line voltage is present.
Transducer malfunction or not installed
If lights are flashing alternatively, then no probe is
connected or the probe is malfunctioning. When using
a pressure transducer, with power applied to the
control, use a voltmeter to measure volts DC between
COMM and P1 or P2, where the wire is connected. The
reading should be according to
Table 3, p. 13
.
The fuse is blown and/or signs of
damage on the unit
Miswired
The unit has been mis-wired and may be permanently
damaged
The fan cycles from ON to OFF with
little or no speed modulation
Improper hard start setting
Reduce hard start setting to minimum needed to
accelerate the fan. Excessive hard start causes large
pressure drops by running too much cold air over the
condenser.
The high pressure switch trips off Improper head pressure setpoint setting
See unit fails to start above.
Check the setpoint and reduce it if needed.
